Dynamic Group can be created as a:
Compartment – all componetns servers, vnc, load balancer, etc which are part of that compartment
Specific Instances
Selection you manage base on Matching Rules which you define
To build Rule use Rule Builder
Define if you want any rule match or all below rules match ( important when you have big network)
For my purpose I will use compartment OCID
Compartment OCID is available from Compartment view
Complete form for Create Rule
Final form for Create Dynamic Group
Dynamic Group Created
You can always edit and update lit of instances in that group.